The present invention relates to a portable, wrist watch type receiver made to be fastened on a wearer's arm and, more particularly, relates to the antenna structure of such a receiver.
There has been proposed a small, portable receiver which employs a whip antenna However, this portable receiver is defective in that its gain decreases when it is used in close proximity to the human body. Another conventional portable receiver is one that uses a loop antenna. When this receiver is used near the human body, the antenna gain increases, but when it is used in free space apart from the human body, that is, when it is not carried on a wearer's arm, the antenna gain decreases In Japanese Patent Public Disclosure Gazette No. 181203/86 (laid open Aug. 13, 1986) there is disclosed a portable receiver of the type wherein a radio unit is housed in the case of a wrist watch and antennas are embedded in its bands. The antennas are each formed by a metal wire extended from the case lengthwise of one of the bands. In the free end portions of the bands where a plurality of small through holes are made for fastening the bands to each other, the metal wires are formed zigzag, passing between the holes in opposite directions. When the wrist watch is fastened on one's wrist, the zigzag portions of the metal wires embedded in the overlapping portions of the bands are electromagnetically coupled together and the metal wires perform the function of a loop antenna as a whole. When the wrist watch is not carried on the arm, the antenna gain is low.
It is disclosed in Japanese Utility Model Public Disclosure Gazettes No. 104810/80, 193773/85 and 132286/82 to hold the antenna of a portable radio receiver in contact with the human body to provide for enhanced sensitivity.